1. Field of the Invention
The present invention relates to a drying apparatus suitable to residential use that can be used compactly, conveniently, and hygienically for drying wet materials requiring dryprocessing such as foodstuffs and raw waste generated in the kitchen, including cooking wastes and leftover food, containing relatively large amounts of moisture.
2. Description of the Prior Art
Drying processes that reduce weight and prevent decomposition are widely used to enable long-term storage of foodstuffs. Other than open-air drying using natural sunlight, foodstuff drying processes using some apparatus include heater drying, forced hot-air drying, microwave drying, freeze-drying, and spray drying methods.
These latter methods play an important role in the foodstuff drying industry because of the ability to dry foodstuffs rapidly when compared with open-air sunlight drying. However, those methods are suitable for the large scaled apparatuses but not for compact apparatuses. One of most compact apparatus utilizing those methods which is really in use is a clothes drier for drying clothes by means of electric power. In this clothes drier, clothes with moisture are held in a drum rotating with respect to a horizontal axis and are blown by a hot air to dry. Since the clothes easily suffer from heat, the hot air should be controlled at a temperature of 70.degree. C. or less. However, water will not boil at thus controlled temperature. Therefore, it is necessary to make the hot air dried. To prepare the dried hot air, the air taken in the apparatus from the outside is heated by the heater to reduce the relative humidity thereof. This relatively dried hot air is blown to the wet clothes to absorb the water vapor from the closes, and hot air containing the water vapor is exhausted the outside. Thus, the clothes are dried.
However, in this type of drying apparatuses, there are following problems. First is that the large sized heat recovering device is necessary to recover the great amount of heat lost together with the exhausted hot air. It is because that a heat recovering rate should be small due the smaller temperature difference between the exhausted air and the outside air. Second is that easily lumping stuffs such as raw wastes from the kitchen can not be dried by thus heated relatively dried air having a lower temperature. Third is that the bad odor from the decomposed stuffs by the drying process is released outside together with the exhausted air.
As with foodstuffs and raw wastes from the kitchen, weight reduction and decomposition prevention have also become desirable for raw wastes generated in the home.
Residential raw wastes are collected by local municipalities, but must be stored for some period in the home until collection because they are not collected every day. During this storage, the raw wastes decompose and begin to smell, the garbage storage site is soiled by garbage fluids, etc., and the garbage itself becomes dirty.
From the perspective of environmental conservation, reducing the amount of garbage has become socially promoted.
Methods for drying raw wastes in the same way as foodstuffs to reduce the volume and prevent decomposition have therefore been proposed. Methods for fermenting raw wastes during the drying process for re-use as fertilizer have also been proposed.
However, devices for drying foodstuffs easily, and devices for successfully drying without decomposing the raw wastes or releasing foul odors are virtually unavailable for residential use, even though many drying apparatuses for industrial use are available.
On the other hand, there are many problems left for the application of drying methods used commercially to residential drying methods.
Evenly drying the process materials is extremely difficult using microwave drying methods with devices having little space inside because of the microwave intensity distribution.
In drying methods using a heater, problems include the extremely long drying time required when the drying temperature is set low to prevent overheating and fire.
Regarding the treatment of odors and waste water produced during drying of foodstuffs and raw wastes, there are no compact drying apparatuses designed for deodorization and waste water treatment, and resolving these concerns has been a major problem.